da* 16-50 f2.8 artificially restricted to f2.8?

Meuh wrote:

The room was dark except for the flash which was firing at the same power between shots, I did have the lens hoods on for all lens but even then the camera was in manual mode and if anything would have tried to boost EV in the wider shots (if it wasn't) because the flash didn't cover the whole room or image frame.

It seems that even wide open my 16-50 is partly closed as I can see the aperture blades wide open even at 50mm and by around 2/3 of a stop which kind of defeats the purpose of a fast zoom as it seems to be preforming closer to an F4 zoom than the f2.8 its meant to be and comparing it to my other f2.8 lens seems to confirm this.